WO2016015382A1 - Conductive ink and preparation method therefor - Google Patents

Abstract

A conductive ink, comprising metal nanometer particles, a dispersing agent, an α-hydroxy polycarboxylic acid and a solvent, wherein the metal nanometer particles have a metal element oxide coating layer with the metal nanometer particles on the surface; and the dispersing agent is a polymer with a polyether main chain skeleton and a terminal active functional group. In the conductive ink, by using the polymer with a polyether main chain skeleton and a terminal active functional group and utilizing a firm anchoring effect of the terminal active functional group with the surface of the metal nanometer particles, the polyether main chain generates a steric hindrance stabilizing effect, agglomeration of the metal nanometer particles is prevented, and the polyether main chain thereof tends to crack and degradate under heat treatment conditions and partially removed by forming a micromolecule product, so that residue is avoided, facilitating the improvement of the electric conductivity of a sintered conducting circuit. Also, by compounding an α-hydroxy polycarboxylic acid, the electric conductivity of the sintered conducting circuit is also improved, and the electric-conduction ink also possesses excellent dispersity and an anti-oxidation property.

Description

Conductive ink and preparation method thereof Technical field

The invention belongs to the technical field of printed electronic inks, and in particular relates to a conductive ink and a preparation method thereof.

Background technique

PrintFullElectronicTechnology is the process of forming conductive traces and graphics, or other electronic devices and systems directly on a substrate using fast, efficient, and flexible printing techniques. The key to the formation of conductive traces and patterns is conductive ink, which is generally composed of metal nanoparticles, a protective agent, a dispersant, a solvent, and other additives.

In order to obtain conductive inks with excellent dispersibility and oxidation resistance of metal nanoparticles, it is often necessary to use more fatty acids, long-chain alkylamines, polyvinylpyrrolidone, polyethyleneimine, polyvinyl alcohol, etc. as metals in the system. A dispersing agent for nanoparticles. In order to improve the adaptability of the conductive ink to different substrates, it is desirable that the conductive ink can achieve low temperature sintering (<300 ° C); however, the dispersant coated on the surface of the metal nanoparticles in the low temperature sintering process is difficult to remove and remains in the conductive line. Affects conductivity. At the same time, the amount of the dispersant added should not be too small. When the dispersant is too thin, the coating layer on the surface of the metal nanoparticles is too thin, which not only can not maintain the dispersibility of the metal nanoparticles, but also reduce the oxidation resistance of the metal nanoparticles. Therefore, the dispersibility of the metal nanoparticles, the oxidation resistance, and the conductivity of the conductive line are extremely difficult. Moreover, in the process of manufacturing, storage or dispersion, the metal nanoparticles inevitably form more or less oxide layers on the surface thereof. If these oxides are not reduced during the sintering process, the conductivity of the conductive lines is inevitably hindered. .

Based on the above drawbacks, the invention patent publication CN1792127A discloses a method of sintering fine copper particles in a reducing organic compound atmosphere, and the reducing organic compound is an alcohol having a hydroxyl group which can be converted into an oxy group or an aldehyde group by oxidation. Class of compounds, while achieving reduction of nano metal particles to enhance conductivity. However, these gaseous reducing substances have flammable and explosive defects and are controlled in the preparation process. The accuracy and difficulty are so great that there is no good means for the dispersion of the metal nanoparticles, the oxidation resistance and the conductivity of the conductive lines in the conductive ink.

technical problem

The purpose of the embodiments of the present invention is to overcome the above-mentioned deficiencies of the prior art, and to provide a conductive ink which has excellent dispersibility and oxidation resistance at the same time, and has less organic residue after low-temperature sintering and excellent conductivity of a conductive line.

Technical solution

In order to achieve the above object, the technical solution of the embodiment of the present invention is as follows:

A conductive ink comprising metal nanoparticles, a dispersant, an α-hydroxy polycarboxylic acid, and a solvent; wherein

The surface of the metal nanoparticle has a metal element oxide coating layer of the metal nanoparticle;

The dispersant is a polymer having a polyether backbone skeleton and a terminal reactive functional group.

The conductive ink of the present invention forms a strong anchoring effect on the surface of the metal nanoparticle by using a polymer having a polyether main chain skeleton and a terminal reactive functional group, and the polyether main chain generates a steric stabilization effect, preventing the metal from being blocked. The agglomeration between the nanoparticles, and the polyether main chain is susceptible to fracture degradation under heat treatment conditions, forming a small molecular product and partially removing, and avoiding the residue is advantageous for improving the conductivity of the fired conductive line. At the same time, the α-hydroxy polycarboxylic acid is further compounded, because of its ionic property and reducibility, it can provide electrostatic stabilization and can reduce the oxide on the surface of the metal nanoparticle during the heat treatment, and is in the range of 150-300 ° C. It can be thermally degraded and removed, thereby improving the electrical conductivity of the fired conductive line while having excellent dispersibility and oxidation resistance.

The invention further provides a method for preparing the above conductive ink, comprising the following steps:

Obtaining metal nanoparticles having an oxide coating on the surface;

The metal nanoparticles are coated with a dispersing agent in a solvent to obtain a preliminary dispersion, wherein the dispersing agent is used in an amount of 50% to 120% of the saturated coating amount of the dispersing agent to the metal nanoparticles;

The α-hydroxypolycarboxylic acid is added to the preliminary dispersion and uniformly dispersed to obtain a conductive ink.

Beneficial effect

According to the above preparation method of the present invention, according to the raw material of the conductive ink of the present invention, the raw material is specifically dispersed stepwise according to its properties in the preparation, and the amount of the conductive ink is dispersed according to the measurement result in the dispersion. The best balance of properties such as conductivity and oxidation resistance.

detailed description

In order to make the objects, technical solutions and advantages of the present invention more comprehensible, the present invention will be further described in detail below with reference to the embodiments. It is understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Embodiments of the present invention provide a conductive ink comprising metal nanoparticles, a dispersant, an α-hydroxy polycarboxylic acid, and a solvent; wherein the dispersant is a polymer having a polyether main chain skeleton and a terminal reactive functional group.

Wherein, the metal nanoparticles of the present invention employ at least one of copper, silver, gold, nickel, aluminum, platinum, palladium or alloys thereof; and the metal nanoparticle surface has an oxide passivation layer of its metal element. The oxide passivation layer is coated on the surface of the metal nanoparticle, in addition to helping to improve the oxidation resistance of the metal nanoparticle, and also helps to improve the adsorption capacity of the anchoring group of the dispersant on the surface of the metal nanoparticle, thereby improving Dispersion stability of metal nanoparticles. The content of the oxide passivation layer on the surface of the metal nanoparticle can be determined by thermogravimetric analysis in an aerobic atmosphere; for the effect of reducing the electrical resistivity of the fired conductive line, it is preferred that the oxide passivation layer occupies the metal nanometer. The mass percentage of the particles is less than 10%. Preferably, the metal nanoparticles used in the present invention have a particle size ranging from 5 to 100 nm; because when the metal nanoparticles have a particle diameter greater than 100 nm, the sedimentation speed of the dispersion is accelerated, and the energy required for sintering is also higher, which is difficult to achieve. Low-temperature sintering; when the particle size of the metal nanoparticles is less than 5 nm, then the specific surface area of these particles becomes large, the activity is higher, the amount of dispersing agent required for achieving stable dispersion is also larger, and the residual organic impurities after sintering are increased. Thereby reducing the electrical conductivity of the fired conductive line.

Further, the above dispersing agent employs a polymer having a polyether main chain skeleton and a terminal reactive functional group, and the polyether main chain skeleton is composed of ethoxy (EO) and/or propoxy (PO) structural units, and terminal activity thereof The functional group is an amino group and/or a carboxyl group. The reactive functional group of the polymer having a polyether main chain skeleton and a terminal reactive functional group, such as an amino group or a carboxyl group, can be adsorbed by forming an organometallic compound or an organometallic complex with an oxide passivation layer on the surface of the metal nanoparticle; The polyether main chain has good flexibility and is easy to oscillate, forming a good steric hindrance, which helps to prevent agglomeration between the metal nanoparticles, thereby improving the dispersibility of the metal nanoparticles; and then adjusting the ethoxylate on the polyether main chain. The ratio of base (EO) to propoxy (PO) can also alter the compatibility of the polymer with the solvent system.

The polymer of the polyether main chain skeleton and the terminal reactive functional group is preferably a polymer having a polyether main chain skeleton and a terminal reactive functional group represented by the following structure for structural linearity and reduction of redox residual effect in the implementation:

Wherein R represents an amino group or a carboxyl group of a reactive functional group, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group, and R ³ represents one of an alkyl group, an alkoxy group, a hydroxyl group and an aldehyde group; And y represents 0 or a positive integer, and x + y ≥ 2; n represents a positive integer greater than 1, and m represents a positive integer.

When the polyether backbone of the polymer contains more CO bonds, the dissociation energy of the CO bond (351 kJ/mol) is more dissociated from the CC bond on the hydrocarbon long-chain polymer (such as polyethylene, polypropylene and polyacrylic resin). The energy (360 kJ/mol) is slightly lower, and therefore, the polymer having a polyether as a main chain is further inferior in thermal stability. If the polyether backbone contains more propoxy (PO), the side methyl group on the propoxy (PO) makes the main chain full of branching points, and the methine hydrogen at the branching point is more easily taken away. And the side methyl group also weakens the bond energy of the CC bond and the CO bond on the polyether main chain, thereby further deteriorating the thermal stability of the polyether main chain. The C-O bond of the polyether backbone begins to undergo thermal cracking at temperatures above 160 ° C. At higher temperatures, the C-C bond can also break. Under anaerobic conditions, the CO bond and CC bond on the polyether main chain undergo direct random split-chain reaction and degradation. The products after thermal degradation include low molecular weight polyether, ethanol, acetaldehyde, propionaldehyde and acetone. , Propylene and other end group structures are thermal degradation products of ketones, aldehydes, alcohols and ethers. Under aerobic conditions, the presence of oxygen atoms in the polyether backbone increases the instability of hydrogen at the alpha carbon atom, except for the CO and CC bonds on the polyether backbone. This makes the polyether backbone more susceptible to thermal oxidation reactions. The above polymer having a polyether main chain skeleton is used as a dispersing agent for the conductive ink, so that it is easily thermally degraded into a volatile small molecule product during sintering, which can reduce the residual amount of organic impurities in the fired conductive line, thereby facilitating the improvement of the conductive The conductivity of the line.

In the above embodiment, it is further preferred that the polymer having a polyether main chain skeleton and a terminal reactive functional group of the present invention has a weight average molecular weight of 500 to 4000; when the weight average molecular weight thereof is less than 500, the steric hindrance is reduced, It is beneficial to improve the dispersibility of metal nanoparticles; when its weight average molecular weight is higher than 4000, the interaction between molecules increases, the molecular chain becomes longer, and the probability of inter-molecule entanglement increases, thereby reducing thermal degradation, which is not conducive to improving firing conductivity. The conductivity of the line.

in use,

The polymer of the structure is polyetheramine of HUNTSMAN Company of the United States.

B-60, B-200, L-100, L-200, L-207, L-300, etc. Another

Structured polymers such as methoxypolyglycolic acid, methoxypolyglycolic acid, methoxypolyethylene glycol amine, alpha-aldehyde-ω-carboxy polyethylene glycol, alpha-aldehyde group- Ω-amino polyethylene glycol, α-carboxy-ω-hydroxy polyethylene glycol, α-amino-ω-hydroxy polyethylene glycol, etc., the specific structure can be seen as follows:

(methoxypolyglycol acetic acid),

(methoxypolyglycolic acid),

(methoxypolyethylene glycol amine),

(α-Amino-ω-hydroxypolyethylene glycol).

Further, the α-hydroxy polycarboxylic acid used in the present invention contains one or more hydroxyl groups in the molecular structure, and two or more carboxyl groups, and at least one carboxyl group has an α-position carbon atom. Have a hydroxyl group. Wherein, the carboxyl group can be adsorbed by forming an organometallic compound or an organometallic complex with an oxide passivation layer on the surface of the metal nanoparticle, and the steric hindrance of the α-hydroxypolycarboxylic acid of these small molecules is not as good as the polyether backbone described above. a polymer with a backbone and a terminal reactive functional group, but which has ionic properties, can charge the surface of the metal nanoparticle, and stabilize the electrostatic repulsion between the metal nanoparticles, thereby preventing agglomeration between the metal nanoparticles; In the case of compounding with a polymer having a polyether main chain skeleton and a terminal reactive functional group and an α-hydroxypolycarboxylic acid, metal nanoparticles can be efficiently dispersed.

At the same time, the α-hydroxy polycarboxylic acid has strong reducibility, and under heating conditions, the oxide on the surface of the metal nanoparticle can be reduced to form a simple metal element having excellent conductivity. More importantly, the α-hydroxypolycarboxylic acid is easily decomposed into a product such as carbon dioxide, carbon monoxide, water and a small molecule carbonyl compound in the range of 150 to 300 ° C, and almost no residue is formed, and the conductivity is not affected; Therefore, the use of the α-hydroxypolycarboxylic acid as a dispersing agent for the conductive ink not only reduces the oxide layer on the surface of the metal nanoparticles, but also reduces the residual amount of organic impurities in the fired conductive line, thereby improving the conductivity of the conductive line.

More preferably, the α-hydroxypolycarboxylic acid molecule used in the present invention has a total carbon number of not more than 10, and the ionic character of the small molecule is relatively better, and it is easier to disperse and thermally degrade. Examples of the α-hydroxypolycarboxylic acid used in the present invention, such as malic acid, tartaric acid, citric acid, 2-hydroxyglutaric acid, 2,3,-dihydroxyglutaric acid, 2,4-dihydroxyglutaric acid , 3-methyl-2,4-dihydroxyglutaric acid, 2,3,4-trihydroxyglutaric acid, and the like.

Finally, in the conductive ink, as the dispersion medium, it is ensured that each material can form a good dispersion as a whole, and it is also necessary to add a solvent; the solvent is used as a dispersion medium in use, and is not particularly limited. But out In order to enhance the effect of the dispersion on the molecular structure and molecular characteristics of the above components, it is preferred to use a polar solvent; it may be selected from the group consisting of alcohols, esters, ketones, alcohol ethers, ether esters, and amides. a mixture of one or more of the classes, and having a boiling point at atmospheric pressure in the range of 60 to 300 ° C, which may eventually volatilize or decompose during sintering to reduce the residue. For example, ethanol, isopropanol, n-butanol, isobutanol, isoamyl alcohol, n-octanol, octanol, cyclohexanol, benzyl alcohol, terpineol, ethylene glycol, diethylene glycol and other alcohol solvents; Ethyl acetate, butyl acetate, butyl propionate, butyl butyrate, γ-butyrolactone, dimethyl succinate, dimethyl glutarate, dimethyl adipate, methyl benzoate, etc. Ester solvent; ketone solvent such as methyl ethyl ketone, methyl isobutyl ketone, 2-hexanone, cyclohexanone, isophorone; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene Alcohol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, digan Alcohol monoether, diglyme, diethylene glycol diethyl ether and other alcohol ether solvents; ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate , propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, diethylene glycol methyl ether acetate, diethylene glycol ethyl ether acetate, diethylene glycol propyl ether Acetate, diethylene glycol Ether ethers such as propyl ether acetate, diethylene glycol butyl ether acetate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate Solvent; amide solvent such as N,N-dimethylformamide, N,N-dimethylacetamide or N-methylpyrrolidone.

By using the conductive ink of the present invention, by using a polymer having a polyether main chain skeleton and a terminal reactive functional group, the terminal reactive functional group forms a strong anchoring action with the surface of the metal nanoparticle, and the polyether main chain generates a steric stabilization effect, preventing The agglomeration between the metal nanoparticles, and the polyether main chain is susceptible to fracture degradation under heat treatment conditions, forming a small molecular product and partially removing, and avoiding the residue is advantageous for improving the conductivity of the fired conductive line. At the same time, the α-hydroxy polycarboxylic acid is further compounded, because of its ionic property and reducibility, it can provide electrostatic stabilization and can reduce the oxide on the surface of the metal nanoparticle during the heat treatment, and is in the range of 150-300 ° C. It can be thermally degraded and removed, thereby improving the electrical conductivity of the fired conductive line while having excellent dispersibility and oxidation resistance.

The invention further provides a method for preparing the above conductive ink, comprising the following steps:

S10, determining a saturated coating amount of the polymer nanoparticle having a polyether main chain skeleton and a terminal reactive functional group;

S20, the metal nanoparticles are coated with a polymer having a polyether main chain skeleton and a terminal reactive functional group in a solvent to obtain a preliminary dispersion; wherein the amount of the polymer having a polyether main chain skeleton and a terminal reactive functional group is a saturated package. 50% to 120% of the coverage;

S30, the preliminary dispersion is redispersed with the α-hydroxypolycarboxylic acid, and then dissolved in the solvent; that is, the conductive ink of the invention is obtained; wherein the α-hydroxypolycarboxylic acid is used in an amount of 1% to 10% by weight of the metal nanoparticles. %.

In the above preparation method of the present invention, the number of polymerizable monomers and reactive groups of the polymer raw material having a polyether main chain skeleton and a terminal reactive functional group is different; in the preparation of the conductive ink in the present invention, in order to disperse The amount of the agent can be used to meet the uniform dispersing amount, and there is no possibility of excessive residue remaining; therefore, in step S10, the saturated coating of the polymer having the polyether main chain skeleton and the terminal reactive functional group is required. The amount is measured because the above-mentioned polymer terminal functional group having a polyether main chain skeleton and a terminal reactive functional group forms a strong anchoring action with the surface of the metal nanoparticle, thereby forming a coating on the nano metal particles. Using this feature, the specific measurement process is:

S11, using an excess of a polymer having a polyether main chain skeleton and a terminal reactive functional group to disperse in a solvent to sufficiently coat the metal nanoparticles to obtain a dispersion;

S12, removing excess polymer having a polyether main chain skeleton and a terminal reactive functional group in the dispersion by high-speed centrifugation, ultrafiltration or centrifugal ultrafiltration, and separating the coated metal nanoparticles;

S13, the content of the organic substance on the surface of the metal nanoparticle is determined by thermogravimetric analysis, that is, the saturated coating amount of the polymer to the metal nanoparticle having the polyether main chain skeleton and the terminal reactive functional group.

Then, in step S20, a polymer having a polyether main chain skeleton and a terminal reactive functional group corresponding to a saturated coating amount of 50 to 120% is used to disperse the nano gold particles in a solvent, and the amount of use can be balanced, thereby ensuring The coating is sufficiently dispersed and the amount of residue is also controlled.

Finally, in step S30, 1% to 10% by weight of the metal nanoparticles are added and then dispersed again after the α-hydroxypolycarboxylic acid is added; in this step, the amount of the α-hydroxypolycarboxylic acid is controlled, and the purpose thereof is When the amount of the α-hydroxypolycarboxylic acid is less than 1% by weight of the metal nanoparticles, the oxide on the surface of the metal nanoparticle cannot be sufficiently reduced; when the amount of the α-hydroxypolycarboxylic acid is more than 10% by weight of the metal nanoparticle, More α-hydroxypolycarboxylic acid is more severe in the process of degradation and gasification during sintering, which tends to cause pores or cracks in the conductive film and reduce the compactness of the conductive film.

According to the above preparation method of the present invention, according to the raw material of the conductive ink of the present invention, the raw material is specifically dispersed stepwise according to its properties in the preparation, and the amount of the conductive ink is dispersed according to the measurement result in the dispersion. The best balance of properties such as conductivity and oxidation resistance.

In order to make the above preparation method of the present invention clearer and easier to understand and effect, the following examples are exemplified by various embodiments:

Example 1

S11, 0.75g of polyetheramine

L-207 (EO/PO=33/10, weight average molecular weight 2000, manufactured by HUNTSMAN, USA) was dissolved in 20 g of isopropanol, and 5 g of copper nanoparticles (having an average particle diameter of 45 nm and a maximum particle diameter of less than 100 nm) were added. The surface copper oxide content is about 5% by mass) and ultrasonically dispersed for 20 minutes to make the copper nanoparticles fully

Covered by L-207;

S12 was added with 200 g of isopropyl alcohol, and some of the solvent was filtered off by centrifugal ultrafiltration, and concentrated to a concentration of about 50% by mass of copper nanoparticles; repeated addition of isopropanol and centrifugal ultrafiltration three times, excess

L-207 is removed with the filtrate to obtain a dispersion having a copper nanoparticle content of about 50% by mass, and the copper nanoparticle in the dispersion is separated by using a membrane filter;

S13, a part of the separated copper nanoparticles were dried in a vacuum at 80 ° C for 2 hours, and then treated in a nitrogen atmosphere at 600 ° C for 30 minutes, the weight was calculated, and the weight was found to be reduced by 4.2%; it can be considered that the weight loss is determined by

Caused by thermal degradation of L-207. This shows that

The saturated coating amount of L-207 to copper nanoparticles was 4.2% by mass. A part of the separated copper nanoparticles was dried in a vacuum at 80 ° C for 2 hours, and then treated at 250 ° C for 30 minutes in a nitrogen atmosphere, and a weight loss of 2.0% was found by weight analysis. It is inferred that the surface of the copper nanoparticles is coated.

The thermal degradation rate of L-207 after treatment in a nitrogen atmosphere at 250 ° C for 30 minutes is about 48%;

S20, isopropanol, ethylene glycol butyl ether acetate and diethylene glycol were prepared in a ratio of 3:6:1 to 77.83 g of a mixed solvent, and 0.67 g was added.

L-207 (corresponding to 80% of the saturated coating amount) and 20 g of copper nanoparticles, ultrasonically dispersed for 20 minutes to form a preliminary dispersion;

S30, 1.5 g of citric acid was added to the preliminary dispersion, and the mixture was stirred for 30 minutes to obtain a conductive ink having a copper nanoparticle content of 20% by mass. The resistivity was measured and the results are reported in Table 1.

Example 2

The polyetheramine of Example 1

L-207 was replaced with methoxypolyethylene glycol propionic acid (molecular weight: 2000, manufactured by Jiaxing Bomei Biotechnology Co., Ltd.), and conductive ink having a copper nanoparticle content of 20% by mass was prepared in the same manner as in Example 1. And the resistivity was measured, and the results are reported in Table 1.

Example 3

The polyetheramine of Example 1

L-207 was replaced with methoxypolyethylene glycol amine (molecular weight: 2000, manufactured by Jiaxing Bomei Biotechnology Co., Ltd.), and a conductive ink having a copper nanoparticle content of 20% by mass was prepared in the same manner as in Example 1, and The resistivity was measured and the results are reported in Table 1.

Example 4

The polyetheramine of Example 1

L-207 and citric acid were replaced with methoxypolyethylene glycol propionic acid (molecular weight 2000, manufactured by Jiaxing Bomei Biotechnology Co., Ltd.) and malic acid, respectively. The same preparation method as in Example 1 was used to prepare copper nanoparticles. The conductive ink was 20% by mass, and the specific resistance was measured. The results are shown in Table 1.

Comparative example 1

Prepare 79g mixed solvent in a weight ratio of 3:1 with isopropanol and terpineol, and add 1g of polyvinylpyrrolidine Ketone (PVPK30, average molecular weight is 58000, Sinopharm Chemical Reagent Co., Ltd.) and dissolved, adding 20g of copper nanoparticles (average particle size is 45nm, maximum particle size is less than 100nm, surface copper oxide content is about 5% by mass), ultrasound After dispersing for 20 minutes, a conductive ink having a copper nanoparticle content of 20% by mass was obtained. The resistivity was measured and the results are reported in Table 1.

Comparative example 2

The polyetheramine of Example 1

L-207 was replaced with polyvinylpyrrolidone (PVPK30, average molecular weight: 58,000, Sinopharm Chemical Reagent Co., Ltd.), and a conductive ink having a copper nanoparticle content of 20% by mass was prepared in the same manner as in Example 1, and the resistivity was measured. The results are reported in Table 1.

In each of the above examples, the resistivity was measured by the following method:

The conductive ink was applied onto a polyimide film using an OSP-8 coating bar (manufactured by Japan Aerotech Co., Ltd.), dried in a forced air oven at 100 ° C for 20 minutes, and then treated at 250 ° C in a nitrogen atmosphere. After 30 minutes, the metal nanoparticles were sintered into a conductive film; the film thickness D of the conductive film was measured using a roughness meter SJ-301 (manufactured by Mitutoyo, Japan), and the square resistance R□ of the conductive film was measured by a four-probe method, and the calculation was performed. The resistivity of the conductive film was calculated by the equation ρ = R □ × D. The results are shown in Table 1:

From the data in the above table, the conductive ink of the present invention can be sintered at 300 ° C or lower, and the organic matter remains less after sintering, and the electrical resistance of the fired conductive line is less than 20 μΩcm. In Comparative Example 1, polyvinylpyrrolidone which is hardly thermally degradable was used as a dispersing agent, and the oxide on the surface of the copper nanoparticle was not reduced, and the electrically conductive line of the fired electrode had a high electrical resistivity. In Comparative Example 2, although the oxide on the surface of the copper nanoparticles was reduced using citric acid, there was still some polyvinylpyrrolidone which was hard to be thermally degraded, and the electrical conductivity of the fired conductive wiring was about twice as large as that of the present invention. Therefore, in comparison, the conductive final effect of the conductive ink of the present invention can be considerably improved. And in the above preparation process, all the preparation processes thereof are relatively simple and controllable, compared with the existing preparation methods such as reducing atmosphere, the production process steps and safety and the like are relatively mild, and the process conditions are relatively mild. The control difficulty is greatly reduced.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. Within the scope.

Claims (10)

1. A conductive ink comprising metal nanoparticles, a dispersant, an α-hydroxy polycarboxylic acid, and a solvent; wherein

   The surface of the metal nanoparticle has a metal element oxide coating layer of the metal nanoparticle;

   The dispersant is a polymer having a polyether backbone skeleton and a terminal reactive functional group.
2. The conductive ink according to claim 1, wherein the metal nanoparticles have a particle diameter ranging from 5 to 100 nm.
3. The conductive ink according to claim 1 or 2, wherein the metal nanoparticle surface oxide layer accounts for less than 10% by mass of the metal nanoparticles.
4. The conductive ink according to claim 1 or 2, wherein the polymer having a polyether main chain skeleton and a terminal reactive functional group is a polymer of the following structural formula:

   

   or

   

   Wherein R represents an amino group or a carboxyl group of a reactive functional group, R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or an alkyl group, and R ³ represents one of an alkyl group, an alkoxy group, a hydroxyl group or an aldehyde group; And y represents 0 or a positive integer, and x + y ≥ 2; n represents a positive integer greater than 1, and m represents a positive integer.
5. The conductive ink according to claim 1 or 2, wherein the polymer having a polyether main chain skeleton and a terminal reactive functional group has a weight average molecular weight of 500 to 4,000.
6. The conductive ink according to claim 1 or 2, wherein the α-hydroxyl polycarboxylate The total number of carbon atoms in the acid does not exceed 10;

   and / or

   The α-hydroxypolycarboxylic acid is added in an amount of 1% to 10% by weight based on the weight of the metal nanoparticles.
7. The conductive ink according to claim 1 or 2, wherein the solvent is a polar solvent having an atmospheric boiling point in the range of 60 to 300 °C.
8. The method for preparing a conductive ink according to any one of claims 1 to 7, comprising the steps of:

   Obtaining metal nanoparticles having an oxide coating on the surface;

   The metal nanoparticles are coated with a dispersing agent in the solvent to obtain a preliminary dispersion, wherein the dispersing agent is used in an amount of 50% to 120% of the saturated coating amount of the dispersing agent to the metal nanoparticles;

   The α-hydroxypolycarboxylic acid is added to the preliminary dispersion and uniformly dispersed to obtain a conductive ink.
9. The method of producing a conductive ink according to claim 8, wherein the α-hydroxypolycarboxylic acid is added in an amount of from 1% to 10% by weight based on the weight of the metal nanoparticles.
10. The method for preparing a conductive ink according to claim 8 or 9, wherein before the step of preparing the preliminary dispersion, the method further comprises the step of determining the saturated coating amount of the dispersant to the metal nanoparticles:

    Fully coating the metal nanoparticles with the excess amount of the dispersant in the solvent;

    Removing excess dispersant and separating the coated metal nanoparticles;

    The content of the dispersing agent coated on the surface of the metal nanoparticle is detected, that is, the saturated coating amount of the dispersing agent to the metal nanoparticle.